The invention pertains to isolated neurotrophic factors, designated as ARIA, which are able to induce the formation of ion channels in a surface membrane of a cell. The amino acid sequence of the neurotrophic factors includes an EGF-like domain, and a second amino acid sequence encoded by at least a portion of an exon of the neurotrophic factor gene normally expressed in a neuronal cell, especially a nerve cell. The neurotrophic factor is distinct from, and essentially unrelated to, the chicken prion-like protein previously identified.